JPH1160508A - Production of organofluorine compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing the subject compound by reacting a chloro- or bromo-organic compound with a fluorinating agent in a benzonitrile solvent while preventing formation of, or removing, an acid fluoride of aromatic compound, in order to prevent corrosion resulting from halogen exchanging and also to prevent formation of ionic fluorine known as corrosive substance. SOLUTION: This compound is obtained by reacting a chloro- or bromo- organic compound [e.g. chlorinated or brominated aromatic compound shown by the formula (X is N or the like; (m) is 1 to 5; (n) is 0 to 4; and (m+n) is 1 to 5)] with a fluorinating agent (e.g. potassium fluoride) preferably at 190 to 400 deg.C and approximately 0 to 30 kg/cm<2> in a benzonitrile solvent, in the presence of, e.g. oxide, hydroxide and/or carbonate of alkaline or alkaline-earth metal (e.g. KOH) to prevent formation of an acid fluoride of aromatic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an organic fluorine compound. Specifically, the present invention
The present invention relates to an improvement in a method for producing an organic fluorine compound by a so-called halogenation exchange reaction in which a chloro or bromo organic compound is reacted with a fluorinating agent in a benzonitrile solvent.

[0002]

2. Description of the Related Art The so-called halogen exchange reaction, in which an alkali halide is allowed to act on an aromatic halide to exchange a halogen atom for a fluorine atom, has been known for a long time. At this time, dimethyl sulfoxide (DM
SO), sulfolane (TMSO ₂ ), N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (N
MP), dimethyl sulfone (DMSO ₂ ) and the like, so-called aprotic polar solvents and the like are mainly used, and the halogen exchange reaction is performed at a temperature lower than the boiling point of the solvent [for example,
Ishikawa, Journal of Synthetic Organic Chemistry, vol. 25, p. 808 (1
967), M. Hudlicky, Chemistry of Organic Fluo
rine Compounds 112, 1976, John Wile
y & Sons publishing etc.). In some cases, a phase transfer catalyst such as a crown compound is added to increase the reaction rate.

However, when the halogen exchange reaction is carried out by the above method, an electron-withdrawing group (for example, -CN, -NO ₂
And the like, the halogens of aromatic monohalides and aromatic polyhalides having a halogen substituent at the ortho or para position are easily halogen-exchanged, whereas halogens at the meta position are difficult to halogen-exchange.

[0004] In addition, when a commonly used solvent is used at a high temperature to improve the yield or when used for a long time, a decomposition reaction of the solvent or a side reaction occurs between the solvent and the raw material or product, As a result, the yield cannot be improved.
In addition, it has a disadvantage that it is not easy to use it industrially in the recovery and reuse of the solvent. In order to avoid the drawback that these solvents cannot be used at high temperatures, it is also common to carry out the reaction at a high temperature of 200 to 500 ° C. using an autoclave without a solvent, and to carry out the reaction at 300 ° C. using an autoclave without a solvent. Examples of halogen exchange of tetrafluoroterephthalonitrile from tetrachlorophthalonitrile at a temperature are also described in, for example, Ueda et al., Bull. Chem. Soc. Japa
n Vol. 40, p. 688. However, since no solvent is used, it is difficult to control the temperature by an exothermic reaction, and after the reaction is completed, a large amount of carbides adhere to the container, which is a method difficult to implement industrially.

As a means of solving the above problems, the present inventors have developed a method in which a chlorinated or brominated organic compound is treated with a fluorinating agent in a benzonitrile solvent at a temperature in the range of 190 to 400 ° C. and at least a pressure of a naturally occurring pressure. A method for producing an organic fluorine compound comprising reacting
No. 4,734. In the above method, since the benzonitrile solvent is thermally stable, when the chlorinated or brominated organic compound is halogen-exchanged into the corresponding organic fluorine compound, it is thermally stable even at a high temperature and is not suitable for other solvents. Since there is no side reaction between the solvent and the raw material or product as described above, it can be used in a high temperature range of 190 to 400 ° C., so that the reaction temperature can be raised and the yield can be improved. In addition, there is an advantage that there is no side reaction between the solvent and the raw material or the product as seen in other solvents, and further, by using this solvent, unlike the production method without a solvent, the temperature control is easy and a large amount is obtained. Also has the advantage of preventing the formation of carbides as products,
It has the advantage that the target product can be obtained in high yield in industrial practice.

However, according to the above manufacturing method,
During halogen exchange reaction, acid fluorides of an aromatic compound are 1000 to 8000 ppm based on an organic fluorine compound.
To the extent (equivalent to the amount of fluorine ions) generated during the halogen exchange reaction and in the subsequent manufacturing process, due to the production of hydrofluoric acid (fluorine ions), which is a corrosive substance caused by the acid fluorides of the aromatic compound. There was a problem that equipment and the like were subject to corrosion.

[0007]

An object of the present invention is to provide a novel method for producing an organic fluorine compound.

Another object of the present invention is to provide a method for producing an organic fluorine compound by reacting a chlorinated or brominated organic compound with a fluorinating agent in a benzonitrile solvent, wherein the generation of benzoic acid chloride during the halogen exchange reaction is reduced. It is intended to provide a method for producing an organic fluorine compound which can be prevented.

Still another object of the present invention is to provide a method for producing an organic fluorine compound by reacting a chlorinated or brominated organic compound with a fluorinating agent in a benzonitrile solvent, wherein benzoic acid chloride generated during the halogen exchange reaction is removed. It is intended to provide a method for producing an organic fluorine compound which can be removed.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies on a novel method for producing an organic fluorine compound in order to achieve the above objects, and have completed the present invention.

That is, the above objects of the present invention are as follows:
When producing an organic fluorine compound by reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent, an organic fluorine compound characterized by preventing or removing acid fluorides of an aromatic compound. This is achieved by a manufacturing method.

It is another object of the present invention to provide (2) a method of reacting a chlorinated or bromoorganic compound with a fluorinating agent in a benzonitrile solvent, wherein an alkali metal or alkaline earth metal oxide, The present invention is also achieved by a method for producing an organic fluorine compound, characterized in that a substance and / or a carbonate is present.

Further, the above objects of the present invention are as follows:
After reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent, the reaction solution or the reaction product is treated with an aqueous liquid, and the aqueous layer is separated. Is also achieved.

Further, the above objects of the present invention are as follows:
(4) It is also achieved by the method for producing an organic fluorine compound according to (3), wherein the aqueous liquid is an acidic aqueous liquid.

The above objects of the present invention are achieved by (5) the method for producing an organic fluorine compound according to the above (1) to (4), wherein the chloro or bromo organic compound is a chloro or brominated aromatic compound. Is also achieved.

The above objects of the present invention are as follows:
The method is also achieved by the method for producing an organic fluorine compound according to any one of the above (1) to (5), wherein the fluorinating agent is at least one selected from the group consisting of an alkali metal fluoride and an alkaline earth metal. .

Still further, the above objects of the present invention are as follows:
(7) The present invention is also achieved by the method for producing an organic fluorine compound according to any one of the above (1) to (6), wherein the acid fluorides of the aromatic compound are benzoic acid fluorides.

The above objects of the present invention are also described in the above (1) to (7), wherein (8) the chloro or bromo organic compound is pentachlorobenzonitrile and the organic fluorine compound is pentafluorobenzonitrile. This is also achieved by the method for producing an organic fluorine compound.

Further, the above objects of the present invention are as follows: (9) pentachlorobenzonitrile is reacted with a fluorinating agent in a benzonitrile solvent to obtain pentafluorobenzonitrile, and benzoic acid present in the obtained reaction solution is obtained. Pentafluorobenzoic acid is produced by hydrolyzing an acid fluoride using an acidic aqueous liquid and separating it on the aqueous layer side, and then hydrolyzing the treated pentafluorobenzonitrile in an aqueous sulfuric acid solution to produce pentafluorobenzoic acid. It is also achieved by a method for producing benzoic acid.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The process for producing an organic fluorine compound according to the present invention comprises reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent to produce an organic fluorine compound. It is characterized in that acid fluorides are prevented from being generated or removed.
By preventing or removing the acid fluorides of the aromatic compound, corrosion is prevented during halogen exchange, and when the obtained organic fluorine compound is further subjected to a reaction such as hydrolysis as an intermediate, fluorine as a corrosive substance is used. The effect of preventing generation of ions can be obtained.

One of the methods for producing an organic fluorine compound, which is a means for achieving the object of the present invention, is to react an chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent (hereinafter, this reaction is called halogenation). Exchange reaction), the presence of an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal. The effect of preventing the generation of acid fluorides of an aromatic compound during a halogen exchange reaction by the presence of an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal. It is.

The mechanism of the generation of the acid fluorides of the above aromatic compounds is as follows, taking benzoic acid fluoride as an example.
It is estimated as follows.

[0023]

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The mechanism described above is based on the fact that benzoic acid is generated by a reaction with a benzonitrile solvent due to a small amount of water (about 500 to 1000 ppm) contained in the reaction solution, and further substituted by chloride ions in the reaction solution to form benzoic acid chloride. Benzoyl chloride) and generates a benzoic acid fluoride (benzoyl fluoride, etc.) by a substitution reaction with a fluorinating agent (potassium fluoride, etc.). The amount of benzoic acid fluoride generated is obtained by halogen exchange reaction in terms of fluorine ion. 1000 to the resulting organic fluorine compound
8000 ppm).

Based on the above presumption, the presence of an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal during the halogen exchange reaction,
Benzoic acid chloride can be broken down,
It has been found that generation of acid fluorides of aromatic compounds can be prevented.

Examples of the alkali metal or alkaline earth metal oxides, hydroxides and / or carbonates include alkali metal oxides such as Na ₂ O and K ₂ O;
O, oxides of alkaline earth metals such as CaO, NaOH,
Hydroxides of alkali metals such as KOH, Mg (OH) ₂ ,
Hydroxides of alkaline earth metals such as Ca (OH) ₂ , Na
₂ CO ₃ , K ₂ CO _{3 and} other alkali metal carbonates, M
Examples thereof include carbonates of alkaline earth metals such as gCO ₃ and CaCO ₃ . Among these, alkali metal hydroxides are preferred because of their high effect, and KOH is particularly preferred.

The addition amount of the oxide, hydroxide and / or carbonate of the alkali metal or alkaline earth metal is 50 to 1500 with respect to benzonitrile.
ppm, preferably 100 to 600 ppm. When the addition amount is less than 50 ppm, the effect of preventing the generation of the acid fluorides of the aromatic compound is not sufficient.
If it exceeds 00 ppm, side reactions such as a hydroxylation reaction with the starting material tend to occur, which is not preferable.

According to the method of the present invention, the content of the acid fluoride of the aromatic compound generated during the halogen exchange reaction can be reduced to about 2000 ppm or less based on the product. Thereby, corrosion of a reactor such as a stainless steel container can be prevented.

In the present invention, the acid fluorides of aromatic compounds that can be prevented or removed can include those derived from trace impurities contained in the starting materials other than benzoic acid fluoride. And tetrafluorobenzoic acid fluoride, tetrachlorobenzoic acid fluoride, monochlorobenzoic acid fluoride, monofluorobenzoic acid fluoride, dichlorobenzoic acid fluoride, difluorobenzoic acid fluoride, tetrachlorophthalic acid fluoride, tetrafluorophthalic acid fluoride and the like.

The chloro or bromo organic compound which is a starting material compound in the present invention can be used as long as it has at least one chlorine atom or bromine atom. Further, those in which a part of a chlorine atom or a bromine atom has already been substituted by fluorine can be used. Among these chloro or bromo organic compounds, chloro or brominated aromatic compounds are preferable, and particularly, the following general formula (1)

[0031]

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(Where X is N, CY or C
Z and Y are Cl or Br, Z is F, CN or NO ₂ ,
m is an integer of 1 to 5, n is an integer of 0 to 4, and the sum of m and n is an integer of 1 to 5. Chlor or brominated aromatic compounds of formula (I) are preferred.

Further, among the chlorinated or brominated aromatic compounds represented by the above general formula (1), the general formula (2)

[0034]

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(Where Y is Cl or Br, Z
Is F, CN or NO ₂ , m ′ is an integer of 1 to 6,
n 'is an integer of 0 to 5, and the sum of m' and n 'is 1 to
6 is an integer. ) Or general formula (3)

[0036]

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(Where Y is Cl or Br, Z
Is F, CN or NO ₂ , m is an integer of 1 to 5, n
Is an integer of 0 to 4, and the sum of m and n is an integer of 1 to 5. The chlorinated or brominated aromatic compounds of formula (I) are preferred.

Further, among the chlorinated or brominated aromatic compounds represented by the above general formula (2), particularly, the general formula (4)

[0039]

Embedded image

(Where Y is Cl or Br, m
Is an integer of 1 to 5, n is an integer of 0 to 4, and the sum of m and n is an integer of 1 to 5. ) Or general formula (5)

[0041]

Embedded image

(Where Y is Cl or Br,
m ″ is an integer of 1 to 4, n ″ is an integer of 0 to 3, and the sum of m ″ and n ″ is an integer of 1 to 4. The chlorinated or brominated aromatic compounds of formula (I) are preferred.

Also, among the chlorinated or brominated aromatic compounds represented by the above general formula (3), particularly, the general formula (6)

[0044]

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(Where Y is Cl or Br, m
Is an integer of 1 to 5, n is an integer of 0 to 4, and the sum of m and n is an integer of 1 to 5. ) Or general formula (7)

[0046]

Embedded image

(Where Y is Cl or Br,
m ″ is an integer of 1 to 4, n ″ is an integer of 0 to 3, and the sum of m ″ and n ″ is an integer of 1 to 4. The chlorinated or brominated aromatic compounds of formula (I) are preferred.

Specifically, chlorobenzene, polychlorobenzenes, o-chloronitrobenzene, m-chloronitrobenzene, p-chloronitrobenzene, 2,4-dinitrochlorobenzene, o-chlorobenzonitrile, m-chloronitrobenzene,
-Chlorobenzonitrile, p-chlorobenzonitrile,
2,6-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 3,5-dichloro-2,4,6-trifluorobenzonitrile, 3-chloro-2,4,5,6-
Tetrafluorobenzonitrile, pentachlorobenzonitrile, 3-chlorophthalonitrile, 3,6-dichlorophthalonitrile, 4,5-dichlorophthalonitrile, tetrachlorophthalonitrile, 5-chloroisophthalonitrile, 5-chloro- 2,4,6-trifluoroisophthalonitrile, tetrachloroisophthalonitrile, 1,2
-Dichloroterephthalonitrile, tetrachloroterephthalonitrile, 3-chloropyridine, 2,5-dichloropyridine, 2,3,5-trichloropyridine, 3,5-dichloro-2,4,6-trifluoropyridine , Pentachloropyridine, 5-chloro-3-cyanopyridine, 6-
Chlor-3-cyanopyridine, 5-chloro-2,4,6
-Trifluoro-3-cyanopyridine, 2,4,5,6
-Tetrachloro-3-cyanopyridine, 6-chloro-4
-Cyanopyridine, 2,3,5,6-tetrachloro-4
-Cyanopyridine, 3,4,5,6-tetrachloro-2
-Cyanopyridine and the like and compounds having a bromine atom in place of chlorine in these compounds. Of these, pentachlorobenzonitrile is particularly preferred.

The fluorinating agent used for the halogen exchange reaction is generally an alkali metal fluoride such as cesium fluoride, potassium fluoride, sodium fluoride, lithium fluoride, calcium fluoride, barium fluoride, hydrofluoric acid, or the like. An alkaline earth metal fluoride such as magnesium fluoride or the like is used. In some cases, a fluoride of a transition metal such as antimony fluoride is also used. In the present invention, any commonly used fluorinating agent can be used. Among these, alkali metal fluorides or alkaline earth metal fluorides which are easy to handle and can be easily obtained commercially practically are preferable, alkali metal fluorides are particularly preferable, and potassium fluoride is most preferable.

The fluorinating agent is required to be at least equivalent to a chlorine atom or a bromine atom substituted by a fluorine atom in a chloro or brominated organic compound as a starting material. A suitable range is 1 to 2 moles relative to bromine atoms.

When the above chloro or bromo organic compound is reacted with the above fluorinating agent in a benzonitrile solvent to produce an organic fluorine compound, the reaction is preferably carried out under spontaneous generation pressure. The reaction may be performed by further increasing the pressure with a gas. Usually 190-400
About 0 to about 30 kg / cm ² (gauge pressure) in a temperature range of 230 ° C., and preferably about 1.30 kg / cm ^{2 in} a temperature range of 230 to 360 ° C.
5 to about 22 kg / cm ² (gauge pressure).

The reaction time varies depending on the reaction temperature and starting materials, but is suitably about 2 to 48 hours.

The chloro or bromo organic compound as a raw material may be added to the reaction system in an amount of about 5 to about 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the benzonitrile solvent.

In the above halogen exchange reaction, when the reaction temperature is low and the reaction time is short, some compounds in which chlorine atoms or bromine atoms are not completely exchanged may be partially formed, but benzonitrile as a solvent may be produced. Boiling point (760
mmHg, 191 ° C.), for example, the boiling point of pentafluorobenzonitrile (760 mmHg, 161 ° C.).
° C), the boiling point of pentafluoropyridine (760 mmH
g, 84 ° C.), the target compound can be removed by stripping, and the high-boiling chlorine or bromine-containing fluorine compound is dissolved in the benzonitrile solvent in the kettle. And survive. By reusing the remaining recovered benzonitrile solution as a solvent in the next reaction, the unreacted intermediate chlorine or bromine-containing fluorine compound can be easily converted to the target compound. As described above, the yield of the target compound such as pentafluorobenzonitrile and pentafluoropyridine can be increased by reusing the recovered benzonitrile solvent.

The halogen exchange reaction is preferably carried out under anhydrous conditions as much as possible in order to suppress the generation of the acid fluoride of the aromatic compound by the side reaction and to increase the reaction rate. Therefore, prior to the reaction, it is preferable to add benzene, toluene and the like to distill and remove water as an azeotropic mixture in advance.

In the present invention, in the halogen exchange reaction,
It is preferable that a phase transfer catalyst is further present in the reaction system. That is, the presence of the phase transfer catalyst has the advantage of increasing the reaction rate and shortening the reaction time. Examples of the phase transfer catalyst include crown compounds such as dibenzo-18-crown-6-ether, and a molecular weight of 300-6.
00 polyethylene glycol or the like can be used. The amount of the phase transfer catalyst to be added is 0.01 to 0.25 mol per mol of the chloro or bromo organic compound as the raw material.
Preferably, 0.05 to 0.20 mol is appropriate.

As the organic fluorine compound obtained by the halogen exchange reaction, an organic fluorine compound corresponding to the starting material compound is obtained, and among these, a fluorinated aromatic compound is preferable, and particularly, the following general formula (8)

[0058]

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(Where V is N, CW or C
F and W are Cl, Br, CN or NO ₂ , p is an integer of 0 to 4, q is an integer of 1 to 5, and the sum of p and q is an integer of 1 to 5. )) Are preferred.

Further, among the fluorinated aromatic compounds represented by the general formula (8), the general formula (9)

[0061]

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(Where W is Cl, Br, CN or NO ₂ , p ′ is an integer of 0 to 5, and q ′ is 1 to 6)
And the sum of p ′ and q ′ is an integer of 1 to 6. ) Or general formula (10)

[0063]

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(Where W is Cl, Br, CN or NO ₂ , p is an integer of 0 to 4, q is an integer of 1 to 5, and the sum of p and q is 1 to 5 Is an integer.).

Further, among the fluorinated aromatic compounds represented by the general formula (9), particularly, the general formula (11)

[0066]

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(Where Y is Cl or Br, p
Is an integer of 0 to 4, q is an integer of 1 to 5, and the sum of p and q is an integer of 1 to 5. ) Or the general formula (1
2)

[0068]

Embedded image

(Where Y is Cl or Br,
p "is an integer of 0 to 3, q" is an integer of 1 to 4, and the sum of p "and q" is an integer of 1 to 4. )) Is preferred.

Further, among the fluorinated aromatic compounds represented by the above general formula (10), particularly, the general formula (13)

[0071]

Embedded image

(Where Y is Cl or Br, p
Is an integer of 0 to 4, q is an integer of 1 to 5, and the sum of p and q is an integer of 1 to 5. ) Or the general formula (1
4)

[0073]

Embedded image

(Where Y is Cl or Br,
p "is an integer of 0 to 3, q" is an integer of 1 to 4, and the sum of p "and q" is an integer of 1 to 4. )) Is preferred.

Specifically, fluorobenzene, polyfluorobenzenes, o-fluoronitrobenzene, m-fluoronitrobenzene, p-fluoronitrobenzene,
2,4-dinitrofluorobenzene, o-fluorobenzenitrile, m-fluorobenzenitrile, p-fluorobenzenitrile, 2,6-difluorobenzonitrile, 3,5-difluorobenzonitrile, 3,5-difluoro-2, 4,6-trichlorobenzonitrile, pentafluorobenzonitrile, 3-fluorophthalonitrile, 3,6-difluorophthalonitrile, 4,5-difluorophthalonitrile, tetrafluorophthalonitrile, 5-fluoroisophthalonitrile, 5-chloro −
2,4,6-trifluoroisophthalonitrile, tetrafluoroisophthalonitrile, 1,2-difluoroterephthalonitrile, tetrafluoroterephthalonitrile,
3-fluoropyridine, 2,5-difluoropyridine,
2,3,5-trifluoropyridine, 3,5-difluoro-2,4,6-trifluoropyridine, pentafluoropyridine, 5-fluoro-3-cyanopyridine, 6-
Fluoro-3-cyanopyridine, 5-chloro-2,4,
6-trifluoro-3-cyanopyridine, 6-fluoro-4-cyanopyridine, 2,3,5,6-tetrafluoro-4-cyanopyridine, 3,4,5,6-tetrafluoro-2-cyanopyridine And the like, and compounds useful as intermediates for synthesis of agricultural chemicals, medicines, dyes and the like. Particularly preferred is pentafluorobenzonitrile.

The benzonitrile solvent used in the halogen exchange reaction can be easily separated from the product by distillation, and the recovered benzonitrile can be reused as a solvent.

Next, as another method for producing an organic fluorine compound, which is a means for achieving the object of the present invention, a reaction solution or a reaction product is obtained after reacting a chloro or bromo organic compound with a fluorinating agent. It is characterized by treating with an aqueous liquid and separating an aqueous layer. After the halogen exchange reaction, the reaction solution or the reaction product is treated with an aqueous solution, and the aqueous layer is separated to effectively remove trace amounts of aromatic acid fluorides present in the reaction solution or the reaction product. Is what you can do.

That is, the acid fluorides of the aromatic compound contained in the reaction solution or the reaction product after the halogen exchange reaction are hydrolyzed by boiling with water to form an aromatic compound such as benzoic acid and hydrogen fluoride. Become acid. Aromatic compounds such as benzoic acid, which are decomposition products, are hardly soluble in cold water, but are readily soluble in hot water. Therefore, the treatment liquid after the boiling treatment is separated into an organic layer containing an organic fluorine compound as a target product and an aqueous layer containing a decomposition product of an acid fluoride of an aromatic compound. Therefore, the acid fluorides of the aromatic compound can be removed by separating and removing the aqueous layer while in the high temperature state.

Similarly, the acid fluorides of the aromatic compound are hydrolyzed by adding an acidic aqueous solution and then in the presence of an acidic substance, and separated into an aqueous layer. in this case,
By using a high-concentration acidic aqueous liquid, it becomes possible to hydrolyze at a lower temperature and in a shorter time (for example, 7
If treatment at 0 ° C. for 24 hours is required, treatment at 40 ° C. for 15 hours at 50 ° C. is sufficient, and treatment at 70% sulfuric acid for 3 hours at room temperature will sufficiently hydrolyze. ). Thereby, the acid fluorides of the aromatic compound can be selectively separated and removed.

As the aqueous liquid that can be added to the above reaction liquid or reaction product, water and an acidic aqueous liquid can be used, and an acidic aqueous liquid is preferable. As the acidic aqueous liquid, for example, an aqueous liquid of an inorganic acid such as sulfuric acid, hydrochloric acid, and nitric acid can be used. Particularly preferred is an aqueous solution of sulfuric acid.

When an aqueous sulfuric acid solution is used, the concentration of the acidic aqueous solution is preferably 5 to 80% as a sulfuric acid concentration, and particularly preferably
~ 70% is preferred. When the treatment is performed at a high concentration, the processing temperature can be lowered and the processing time can be shortened. When the reaction is performed at a low concentration, hydrolysis of the reaction product itself can be suppressed.

The treatment temperature is appropriately determined according to the type and concentration of the aqueous liquid to be used. When at least an acidic aqueous liquid is used, the target product is hydrolyzed by the acidic aqueous liquid. It must be performed in a temperature range that is not affected by heat. That is, in this treatment step, the target product is hydrolyzed and easily dissolved in water, so it is eluted into the aqueous layer side, and the eluted product is separated and removed from the reaction solution or reaction product, and the yield is increased. This leads to a decline. Thus, the temperature range is 5 to 130C, especially 10 to 80C
It is better to do it.

The amount of the aqueous liquid to be added to the reaction solution or the reaction product is determined in consideration of the contact effect between the aqueous layer and the organic layer, the efficiency of hydrolysis of acid fluoride, and the ease of separation of the aqueous layer and the organic layer. Then, the amount is 30 to 600 parts by weight, preferably 50 to 300 parts by weight, based on 100 parts by weight of the organic fluorine compound in the reaction solution or the reaction product. Organic fluorinated compounds, which are the desired products to be obscured (intermediates for synthesis)
Is further hydrolyzed by boiling in an acidic aqueous liquid,
It can be a final product as one kind of useful compounds such as agrochemicals, medicines, dyes, or other intermediates for synthesis. However, when acid fluorides of an aromatic compound are present in such a production process, the aromatic compound Acid fluorides are also hydrolyzed to generate hydrofluoric acid (fluorine ion) as a corrosive substance, which corrodes reaction equipment (equipment), etc., so that acid fluorides of aromatic compounds are removed before the production process. It is necessary to do it. A waste acid aqueous solution after completion of the next step (hydrolysis step) can be used as it is as the acidic aqueous liquid. In that case, for example, when the acidic substance is sulfuric acid, ammonium sulfate is contained. In addition, the target substance remaining in the waste acid can be recycled and used effectively as it is.

Here, the reaction product refers to a reaction solution obtained by reacting a chloro or bromo organic compound with a fluorinating agent without using the means for removing the acid fluorides of the aromatic compound according to the present invention. , An organic fluorine compound as a target product obtained by separation and purification by a conventionally known means such as distillation. Therefore, the reaction product mentioned here contains acid fluorides of aromatic compounds.

Next, the process for producing pentafluorobenzoic acid according to the present invention comprises: (1) reacting pentachlorobenzonitrile with a fluorinating agent in a benzonitrile solvent to obtain pentafluorobenzonitrile; The benzoic acid fluoride present in the obtained reaction solution is hydrolyzed using an acidic aqueous solution and separated on the aqueous layer side. (3) Then, the treated pentafluorobenzonitrile is hydrolyzed in an aqueous sulfuric acid solution to obtain pentafluorobenzene. It is characterized by producing benzoic acid.

The method for producing pentafluorobenzoic acid can be said to be a preferred embodiment utilizing the above-described method for producing an organic fluorine compound. Therefore, if necessary,
As a means for preventing the generation of acid fluorides of an aromatic compound, an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal may be present during the halogen exchange reaction.

When performing the hydrolysis reaction of pentafluorobenzonitrile in an aqueous sulfuric acid solution, the reaction is preferably carried out under normal pressure. Alternatively, the reaction may be carried out under spontaneous pressure using a pressure-resistant device. Usually, it is good to carry out in a temperature range of 100 to 200 ° C, preferably 130 to 170 ° C. The reaction time varies depending on the reaction temperature and the sulfuric acid concentration.
It is desirable to carry out the reaction for a period of up to 48 hours, preferably 5 to 24 hours. The concentration of sulfuric acid is usually in the range of 40 to 85%, preferably 55 to 75%.

After completion of the reaction, the obtained pentafluorobenzoic acid has a low solubility in a sulfuric acid aqueous solution at room temperature. Therefore, it can be usually separated from the aqueous sulfuric acid solution by cooling and filtering.

Since the filtered cake contains sulfuric acid and ammonium sulfate, it is preferable to wash the cake with water. Since the target substance, pentafluorobenzoic acid, is dissolved in the washing water, it can be appropriately recycled to the reaction solution and used. Further, it can be used as a cleaning solution for the next lot. By such recycling, the loss of pentafluorobenzoic acid can be prevented, and the amount of wastewater can be reduced.

The method of hydrolysis and treatment with sulfuric acid are described in phthalonitriles, for example, 3,4,5,6
The same applies to the method of hydrolysis of tetrafluorophthalonitrile.

Hereinafter, a method for producing pentafluorobenzoic acid will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing a preferred embodiment of a production apparatus used in the method for producing pentafluorobenzoic acid of the present invention. As shown in FIG. 1, in the method for producing pentafluorobenzoic acid of the present invention, pentachlorobenzonitrile (PCBN), benzonitrile (B
N) Solvents, fluorinating agents (KF) and, if necessary, oxides, hydroxides and / or carbonates (KOH) of alkali metals or alkaline earth metals for the purpose of preventing the generation of acid fluorides of aromatic compounds Is supplied to the halogen exchange reactor 15 through each of the pipes 11 to 14. In the reaction device 15, pentachlorobenzonitrile is reacted with a fluorinating agent in a benzonitrile solvent to obtain pentafluorobenzonitrile. The details of this reaction step are the same as those described in the method for producing an organic fluorine compound. In particular, in the present invention, from the viewpoint of preventing the generation of acid fluorides of an aromatic compound, it is preferable to carry out the reaction in the presence of an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal. Thereby, corrosion at the time of halogen exchange can be prevented.

The obtained reaction solution is sent to an evaporator 17 through a pipe 16. In the evaporator 17, potassium chloride (KCl) and unreacted fluorinating agent (KF), which are relatively easily separated from the reaction solution, are separated as residues by a crude distillation operation. The residue is removed through a pipe 18. In this step, potassium chloride (KCl)
By separating and removing the unreacted fluorinating agent (KF) as a residual component, it becomes possible to reuse the high-boiling component separated in the subsequent distillation step as a recovered benzonitrile solvent.

Next, the separated liquid from which the residue has been removed from the reaction liquid is sent to a precision fractionating apparatus 20 through a pipe 19. In the precision fractionation apparatus 20, 3,5-dichloro-2,4,6-
Trifluorobenzonitrile, 3-chloro-2,4,
A high-boiling chlorine-containing fluorine compound such as 5,6-tetrafluorobenzonitrile dissolves in a benzonitrile solvent and remains. The remaining high-boiling components are circulated through the pipe 21 and reused as a recovered benzonitrile solvent. As a result, the chlorine-containing fluorine compound as an unreacted intermediate can be easily changed to pentafluorobenzonitrile (PFBN) as the target compound, and the yield of the target compound can be increased.

The low-boiling component (light fraction) of pentafluorobenzonitrile containing benzoic acid fluoride
Is sent to an acid fluoride treatment device 23 through a pipe 22. In the acid fluoride treatment device 23, a pipe 24
(In the case where waste sulfuric acid after hydrolysis in the next step is used, containing ammonium sulfate, PFBN and PFBA), only the benzoic acid fluoride present in the low boiling components is hydrolyzed. Separate to the water layer side. After the treatment, an aqueous layer containing benzoic acid and hydrofluoric acid, which are components for decomposing benzoic acid fluoride, is separated and removed through the pipe 25. By this operation which is a characteristic part of the present invention,
Since benzoic acid fluoride is removed, it is possible to prevent the generation of fluorine ions as a corrosive substance caused by benzoic acid fluoride when pentafluorobenzonitrile is hydrolyzed in the next step.

The treated pentafluorobenzonitrile taken out as an organic layer is sent to a hydrolysis reactor 27 through a pipe 26. The hydrolysis reaction device 2
At 7, pentafluorobenzonitrile is hydrolyzed in an aqueous sulfuric acid solution (H ₂ SO ₄ aq) supplied through a pipe 28 to produce pentafluorobenzoic acid.

[0097] The solution after the treatment is sent to the filtration and washing unit 30 via the pipe 29. In the filtration and washing section 30, the solution after the treatment is filtered, and the separated filter cake is sufficiently washed with washing water (H ₂ O) sent through a pipe 34, and
It is sent to the drying section 32 through 1. In the drying section 32,
Dry the thoroughly washed filter cake to obtain the desired pentafluorobenzoic acid (PFBA). Further, the waste sulfuric acid (including ammonium sulfate, PFBN, and PFBA) of the filtrate is supplied to the acid fluoride treatment device 23 through the pipe 24, and can be reused as an acidic aqueous liquid. Further, the washing liquid after washing the filter cake is sent from the pipe 33 to the hydrolysis reactor 27 via the pipe 28, and can be recycled and used as the reaction liquid. Alternatively, a saturated aqueous solution of PFBA can be used again as the cleaning solution for the next lot via the pipe 35 via the pipe 35. Further, a part thereof is discharged as waste liquid through the pipe 36. In addition, the method for producing pentafluorobenzoic acid is as follows. And then 3,
The present invention can be similarly applied to a method of producing 3,4,5,6-tetrafluorophthalic acid by hydrolyzing 4,5,6-tetrafluorophthalonitrile with an aqueous sulfuric acid solution.

[0098]

【Example】

Example 1 190 g of benzonitrile, 66.1 g (0.24 mol) of pentachlorobenzonitrile, 83.7 g (1.44 mol) of finely divided dry potassium fluoride and potassium hydroxide were placed in an autoclave of a 500 cc stainless steel container (SUS316). After charging 0.084 g and replacing the air in the reaction vessel with nitrogen gas, the mixture was heated and stirred at 315 ° C. for 18 hours. After completion of the reaction, potassium chloride and unreacted potassium fluoride were separated from the reaction solution under the final conditions of an external temperature of 200 ° C. and a degree of vacuum of 20 Torr using a rotary evaporator.

Using a precision fractionation apparatus, the separated product was purified using pentafluorobenzonitrile (normal pressure: 161 to 162).
33.3 g could be recovered. When benzoic acid fluoride in the recovered pentafluorobenzonitrile was analyzed by gas chromatography, it was found that 0.039
g of benzoic fluoride (vs. 1170 ppm of pentafluorobenzonitrile) was found to be present. In addition, the corrosion property of the stainless steel container was not recognized.

Comparative Example 1 The procedure of Example 1 was repeated except that potassium hydroxide was not added.
The same procedure as in Example 1 was carried out, the reaction was carried out in the same manner, and the reaction was worked up. As a result, 35.9 g of the target product pentafluorobenzonitrile (fraction at atmospheric pressure of 161 to 162 ° C.)
Could be recovered. When benzoic acid fluoride in the recovered pentafluorobenzonitrile was analyzed by gas chromatography, 0.21 g of benzoic acid fluoride (based on pentafluorobenzonitrile 5850 pp) was analyzed.
m) was found to be contained. In addition, some corrosiveness was confirmed in the stainless steel container.

Example 2 The pentafluorobenzonitrile 30 obtained in Example 1 was obtained.
20 g of a 70% sulfuric acid solution was added to the resulting mixture, followed by stirring at room temperature for 3 hours. Next, after standing still, an organic layer (pentafluorobenzonitrile layer) and an aqueous layer were separated. When the organic layer was analyzed, no benzoic acid fluoride was detected.

Example 3 To 30 g of pentafluorobenzonitrile (containing 1400 ppm of benzoic acid fluoride) obtained by the same method as in Example 1, 60 g of a 50% sulfuric acid solution was added, followed by stirring at 40 ° C. for 23 hours. Next, after standing still, an organic layer (pentafluorobenzonitrile layer) and an aqueous layer were separated. When the organic layer was analyzed, benzoic acid fluoride was 0.0046 g.
(To 153 ppm of pentafluorobenzonitrile).

Example 4 60 g of a 20% sulfuric acid solution was added to 30 g of pentafluorobenzonitrile (containing 1210 ppm of benzoic acid fluoride) obtained by the same method as in Example 1, and the mixture was stirred at 50 ° C. for 24 hours. Next, after allowing to stand still, an organic layer (pentafluorobenzonitrile layer) and an aqueous layer were separated. When the organic layer was analyzed, no benzoic acid fluoride was detected.

Example 5 60 g of water was added to 30 g of pentafluorobenzonitrile (containing 950 ppm of benzoic acid fluoride) obtained by the same method as in Example 1, and the mixture was stirred at 70 ° C. for 24 hours. Next, after standing still, an organic layer (pentafluorobenzonitrile layer) and an aqueous layer were separated. When we analyzed the organic layer,
No benzoic acid fluoride was detected.

Example 6 Pentafluorobenzonitrile 2 treated in Example 4
A sulfuric acid solution prepared by mixing 6.5 g, 35.0 g of concentrated sulfuric acid and 36.5 g of water was charged into a 300 cc glass flask, and reacted at a temperature of 145 to 165 ° C. for 15 hours. Thereafter, the obtained reaction solution was filtered, and the separated cake was sufficiently washed with a washing solution saturated with pentafluorobenzoic acid, and then the cake was dried. As a result, 29.1 g of pentafluorobenzoic acid was obtained. In addition, the result of examining the glass flask used after the reaction. No devitrification was observed, and no corrosion of the glass was confirmed.

Comparative Example 2 The procedure of Example 6 was repeated, except that pentafluorobenzonitrile (containing 1150 ppm of benzoic acid fluoride) obtained in the same manner as in Example 1 was used. Processed. As a result, the glass flask used after the reaction was examined. As a result, devitrification was observed throughout the flask, and it was confirmed that the glass was clearly corroded.

Example 7 30 g of pentafluorobenzonitrile obtained by the same method as in Example 1 (1400 ppm of benzoic acid fluoride)
The waste sulfuric acid aqueous solution 60 g (H ₂ SO ₄
27.6% by weight, 5.3% by weight of (NH ₄ ) ₂ SO _{4 and} 0.7% by weight of pentafluorobenzoic acid).
Stirred at C for 24 hours. Next, after standing still, an organic layer (pentafluorobenzonitrile layer) and an aqueous layer were separated.
When the organic layer was analyzed, no benzoic acid fluoride was detected.

Example 8 In Example 1, 3,4,5,6-tetrachlorophthalonitrile 8 was used instead of pentachlorobenzonitrile.
0.0 g (0.301 mol) and the same procedure as in Example 1 except that 0.1 g of sodium hydroxide was used instead of potassium hydroxide, and the reaction was carried out at 270 ° C. for 16 hours. After completion of the reaction, the mixture was cooled to room temperature, and the suspended potassium chloride and unreacted potassium fluoride were removed by filtration. The benzonitrile solution of the mother liquor was analyzed by gas chromatography to find that 3,4,5,6-tetrafluorophthalonitrile was 55.4 g and 0.01%.
It was found to contain 8 g of benzoic fluoride (325 ppm of 3,4,5,6-tetrafluorophthalonitrile). In addition, the corrosion property of the stainless steel container was not confirmed.

Comparative Example 3 The procedure of Example 7 was repeated, except that sodium hydroxide was not added.
Post-reaction treatment was analyzed in the same manner. As a result, it was found that the benzonitrile solution of the mother liquor contained 0.200 g of benzoic acid fluoride (3,4,5,6-tetrafluorophthalonitrile relative to 3600 ppm). In addition, some corrosiveness was confirmed in the stainless steel container.

Example 9 100 g of a benzonitrile solution of the mother liquor obtained in Example 8
To the mixture was added 80 g of a 70% sulfuric acid solution, and the mixture was stirred at room temperature for 2 hours. Next, after standing still, an organic layer (benzonitrile solution layer) and an aqueous layer were separated. When the organic layer was analyzed, no benzoic acid fluoride was detected.

[0111]

According to the present invention, corrosion during fluorinated halogen exchange can be prevented.

Furthermore, the generation of fluorine ions as corrosive substances can be prevented in the hydrolysis step following the halogen exchange reaction step.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a preferred embodiment of a production apparatus used in the method for producing pentafluorobenzoic acid of the present invention.

[Explanation of symbols]

11 to 14, 16, 18, 19, 21, 22, 24 to 2
6, 28, 29, 31, 33 to 36 ... piping,
15: halogen exchange reaction device, 17: evaporator, 20: precision fractionation device, 23:
Acid fluoride treatment device, 27: hydrolysis reaction device, 30: filtration and washing unit, 32: drying unit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07C 63/70 C07C 63/70 253/30 253/30 255/50 255/50 C07D 213/61 C07D 213/61 213/84 213 / 84 // C07B 61/00 300 C07B 61/00 300

Claims (9)

[Claims] 1. An organic fluoride compound produced by reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent to prevent or eliminate the generation of acid fluorides of aromatic compounds. For producing an organic fluorine compound. 2. When reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent, the presence of an oxide, hydroxide and / or carbonate of an alkali metal or alkaline earth metal is determined. A method for producing an organic fluorine compound. 3. An organic fluorine compound comprising reacting a chloro or bromo organic compound with a fluorinating agent in a benzonitrile solvent, treating the reaction solution or reaction product with an aqueous liquid, and separating an aqueous layer. A method for producing a compound. 4. The method for producing an organic fluorine compound according to claim 3, wherein the aqueous liquid is an acidic aqueous liquid. 5. The method according to claim 1, wherein the chloro or bromo organic compound is a chloro or brominated aromatic compound. 6. The method for producing an organic fluorine compound according to claim 1, wherein the fluorinating agent is at least one selected from the group consisting of alkali metal fluorides and alkaline earth metals. 7. The method for producing an organic fluorine compound according to claim 1, wherein the acid fluorides of the aromatic compound are benzoic acid fluorides. 8. The method for producing an organic fluorine compound according to claim 1, wherein the chloro or bromo organic compound is pentachlorobenzonitrile and the organic fluorine compound is pentafluorobenzonitrile. 9. Reacting pentachlorobenzonitrile with a fluorinating agent in a benzonitrile solvent to obtain pentafluorobenzonitrile, and hydrolyzing benzoic acid fluoride present in the obtained reaction solution using an acidic aqueous solution A process for producing pentafluorobenzoic acid, comprising separating pentafluorobenzonitrile after treatment in an aqueous solution of sulfuric acid to produce pentafluorobenzoic acid.